1. Field of the Invention
This invention concerns light source systems, and more specifically a polarized light source system with a pair of prism plates and a liquid crystal display (LCD) using the same.
2. Description of Related Art
Most users of portable devices such as laptop and notebook computers, mobile phones and game devices expect the viewing screens thereof to be large, clear and bright. Performance equal to that of cathode-ray tube (CRT) desktop monitors is desired. LCDs are one type of flat panel display (FPD) which can satisfy these expectations. However, because liquid crystals are not self-luminescent, LCDs need an illuminator which offers sufficient luminance (brightness) for a planar surface.
Referring to FIG. 4, a conventional LCD 10 comprises a backlight system 12, a thin film transistor (TFT) substrate 14, a color filter substrate 16, liquid molecules 18 between the substrates 14, 16, and a pair of polarizers 19, 19′ having optical axes perpendicular to each other. The backlight system 12 includes a light guide plate 122, a light source 124, and a light source reflector 126. Light emitted from the light source 124 enters a side of the light guide plate 122 and emits uniformly from a top surface of the light guide plate 122.
The light emitted from the light source 124 consists of p-polarized and s-polarized lights. In operation, the light is transported by light guide plate 122 into the polarizer 19. The polarizer 19 allows only one kind of p-polarized light polarized along an optical axis thereof to pass therethrough. Generally, at least 50% of the light is lost at the polarizer 19. The p-polarized light passes through the iTT substrate 14, liquid molecules 18 and the color filter substrate 16 in turn, with the result that no more than 20% of the light emitted from the light source 124 is used. That is, the efficiency of use of the light source 124 is no more than 20%.